Cable-operated doors such as garage doors are well known in the art. A garage door is usually connected to an overhead counterbalancing mechanism that provides a counterbalancing force in order to decrease the force required to open the door and also facilitate its closing. A conventional garage door is typically connected to the counterbalancing mechanism by means of two cables, one at the right and one at the left. The cables are usually made of steel. The lower free end of each cable is usually attached at the bottom of the door.
It is also known in the art that a garage door needs to have a proper counterbalancing system so that it may be easily opened and closed. The counterbalancing force is generally achieved by the usage of either one or many torsional springs. Each torsional spring is generally connected to two plugs, a first one being the “winding plug” at one end of the spring, and a second one being the “stationary plug” at the other end of the spring. The winding plug is generally in turn fixed onto the shaft while the stationary plug is generally fixed onto a fixed structure, such as a bearing plate mounted to a wall for example. To transmit the force to the door, there are generally two drums on the shaft of the counterbalancing mechanism on which cables are installed. The extremities of these cables are generally fixed onto bottom brackets, one on each side (left and right) of the door, typically at the last or bottom panel of a sectional door for example.
One could envisage that, although very unlikely, it might happen that one of the elements (e.g. spring) of the counterbalancing mechanism which are operatively connected to the cables may undergo a failure, leading to the garage door falling, which is undesirable. There have been other attempts to come up with braking devices used in the event of a failure of a cable or of an element holding the same.
Known in the art are the following US and foreign patents/patent applications which describe various cable braking devices for garage doors and the like: U.S. Pat. Nos. 4,385,471; 5,090,522; 5,291,686; 5,581,939; 6,279,268B1; 6,553,716 B2; U.S. Pat. No. 6,640,496 B2; U.S. Pat. No. 6,715,236 B2; US 2002/0117787 A1; US 2003/0000655 A1; and FR 2,697,570.
However, most of the devices comprise detecting means which detect a loss of tension in the cable by means of levers, linkages, and the like which are either displaced along the same direction of the cable or in a direction perpendicularly thereto, which does not always enable a direct and sudden braking capability upon detection of the loss of tension in the cable. Furthermore, in order to carry out their braking functions, most of the above-mentioned devices rely on cams, and the like, which are used to frictionally engage or clamp a given portion of a side rail so as to brake the cable-operated door with respect to such a fixed structure. However, the braking capabilities of such devices rely mainly on the particular shape and eccentricity of the given cam.
Hence, in light of the above-discussed, there is a need for an improved brake device which would be able to overcome some of the aforementioned prior art problems.